What is curing of rubber?

Curing, also known as vulcanization, causes the long polymer chains that rubber is composed of to become crosslinked. This prevents the chains from moving independently, allowing the material to stretch under stress and then return to its original shape when the stress is released.

What is cure time of rubber?

For soft rubber, a one hour cool down is sufficient 7. For semi-hard, hard and tri-ply linings, and gradual cool down is required to prevent cracking. A three hour step process is best.

What is curing of elastomers called?

Vulcanization or crosslinking or curing is an essential part of processing of an elastomer product. It is the final stage in processing, and it helps in improving the elastic strength, solvent resistance and oxidation resistance of elastomers [1].

What is the process of hardening rubber?

Vulcanization (British: Vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice.

What is vulcanization of a rubber?

Vulcanization is a chemical process in which the rubber is heated with sulphur, accelerator and activator at 140–160°C. The process involves the formation of cross-links between long rubber molecules so as to achieve improved elasticity, resilience, tensile strength, viscosity, hardness and weather resistance.

Vulcanization of Rubber | 12th Std | Chemistry | Science | CBSE Board | Home Revise

Why sulphur is used in vulcanization?

Vulcanization of rubber involves heating it in the presence of sulphur. This results in cross-linking of the chains of rubber and sulphur to form a stable polymer which is more strong and stable.

What is the difference between rubber and vulcanized rubber?

Natural rubber is the latex of rubber tree that has a mixture of polymers, while vulcanized rubber is the material that forms after the vulcanization of natural rubber. The key difference between natural rubber and vulcanized rubber is in their mechanical properties.

Why sulphur is added to rubber?

Mineral sulfur is a widely used ingredient to form cross-links between the rubber chains in the vulcanization process. During compounding, a high elastic state of sulfur at temperatures between 40°C and 70°C promotes elongation of its particles and, next, breaking these thin and weak needles into pieces.

Which component is used to harden the rubber?

Which component is used to harden the rubber in the vulcanization process? Notes: Vulcanization is a chemical process that converts natural rubber and other polydiene elastomers into cross-linked polymers. The most common vulcanization agent is sulfur.

What's the meaning of Vulcanize?

Definition of vulcanization

: the process of treating crude or synthetic rubber or similar plastic material chemically to give it useful properties (such as elasticity, strength, and stability)

What is a curing process?

Curing is a process during which a chemical reaction (such as polymerization) or physical action (such as evaporation) takes place, resulting in a harder, tougher or more stable linkage (such as an adhesive bond) or substance (such as concrete).

Why curing is done?

Curing plays an important role on strength development and durability of concrete. Curing takes place immediately after concrete placing and finishing, and involves maintenance of desired moisture and temperature conditions, both at depth and near the surface, for extended periods of time.

What are the purpose of curing?

Curing serves these main purposes: It retains moisture in the slab so that the concrete continues to gain strength. It delays drying shrinkage until the concrete is strong enough to resist shrinkage cracking. Properly curing concrete improves strength, durability, water tightness, and wear resistance.

What is a curing period?

Cure time is the time that determines how long things take to fully cure. A series of chemical reactions occurs during cure time. These chemical reactions allow things to set, harden and develop traits. It may take weeks, months or years. Many factors have an impact on the curing time of a product.

What does cure time mean?

The cure time is the time that it takes from mixing the two part epoxy until the composite has reached full strength, full chemical resistance, and full temperature resistance capability. This time is required to ensure the repair meets the minimum strength requirements to which it was designed.

How do you measure cure?

Rheometers are used to evaluate the degree of hardening through changes in viscosity during the curing process. The adhesive changes from a liquid to a solid during the curing process. The phenomenon during curing where the adhesive solidifies indicates a change in viscosity, and therefore, a change in viscoelasticity.

What chemicals are added to rubber?

Both carbon black and silica, when added to a mix compound at a concentration of about 30 percent by volume, raise the elastic modulus of the rubber by a factor of two to three. They also confer remarkable toughness, especially resistance to abrasion, on otherwise weak materials such as SBR.

What are activators in rubber?

The vulcanization of rubber is a chemical process to improve the mechanical properties by cross-linking unsaturated polymer chains. Zinc oxide (ZnO) acts as an activator, boosting the rubbers' sulfur vulcanization.

What are vulcanizing agent?

Vulcanization agents: These materials are necessary for vulcanization processes where chemical crosslinks are introduced into the rubber matrix to form a three-dimensional network. From: Shreir's Corrosion, 2010.

Why is it called vulcanizing?

The Roman god Vulcan (whose Greek counterpart is Hephaestus) was the god of fire and of skills that used fire, such as metalworking. So when Charles Goodyear discovered that high heat would result in stronger rubber, he called the process "vulcanization" after the god of fire.

Why is sulphur used in tyre?

Insoluble sulphur is mainly used as a vulcanisation accelerator and agent in the rubber industry. It allows a more solid adhesion of the rubber, prevents the rubber from breaking apart and improves resistance to heat and tyre wear, and is therefore an essential raw material in tyre production.

Which chemical is used for vulcanization of rubber?

Vulcanization gives rubber its characteristic elastic quality. This process is carried out by mixing the latex with sulphur (other vulcanizing agents such as selenium and tellurium are occasionally used but sulphur is the most common) and heating it in one of two ways.

What is difference between natural rubber and synthetic rubber?

Natural rubber is produced naturally from the native Brazilian plant Hevea brasiliensis. Synthetic rubber is artificially produced from a variety of polymers which provides the rubber its properties.

Is natural rubber vulcanized?

Natural rubber is produced from latex - milky emulsion drawn from the rubber tree (Hevea brasiliensis) or some other plants. When coagulated latex transforms into soft, plastic and sticky substance (crude rubber), which is then vulcanized (cured). Natural rubber is composed of polyisoprene molecules.

What is accelerator in vulcanization?

An accelerator is defined as the chemical added into a rubber compound to increase the speed of vulcanization and to permit vulcanization to proceed at lower temperature and with greater efficiency.